Modular CPAP compressor

ABSTRACT

A modular compressor assembly comprises a common motor assembly, an impeller, a blower housing and an engagement mechanism. The common motor assembly includes a stator housing containing a stator assembly and having a rotor magnet rotatably disposed therewithin. The impeller is mounted to and rotatable with the rotor magnet. The blower housing is selectable from among a plurality of blower housings each having a different cross-sectional geometry. The engagement mechanism is formed on the stator housing and/or the blower housing and allows interchangeable mounting of different blower housing configurations to the common motor assembly in order to achieve varying flow characteristics of the compressor assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

(Not Applicable)

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

(Not Applicable)

BACKGROUND

The present invention relates generally to patient ventilation systemsand, more particularly, to a modular compressor assembly which can beassembled using a baseline or common motor assembly to which can bemounted various sizes and configurations of blower housings in order toachieve different flow capabilities for the compressor assembly.

Blowers are commonly used in mechanical ventilators to generatecompressed air for delivery to a patient. Such blower assemblies maycomprise a blower housing having a blower inlet and a blower outlet. Theblower assembly includes a motor assembly mounted within the blowerhousing and which is coupled to an impeller which draws air into theblower inlet. The air is compressed as it flows through the impeller andenters an annular chamber or volute after which the air is dischargedfrom the blower outlet.

The motor assembly may be provided in a variety of alternativeconfigurations such as a conventional brushed D.C. motor or in abrushless configuration. Because of their high operating efficiencyunder low-load conditions, brushless D.C. motors are particularlywell-suited for use in generating compressed air. As such, brushlessD.C. motors are commonly used in miniature fans and other blowerconfigurations including certain ventilatory applications such as inCPAP devices for treating obstructed sleep apnea (OSA).

A further advantage of employing brushless D.C. motors in blowerassemblies for CPAP devices is the reduced amount of vibration, heat andnoise generated during operation which allows the use of CPAP devices insensitive environments such as intensive care units (ICU) rooms or in abedroom of a respiratory care patient. Furthermore, compressorassemblies powered by brushless D.C. motors may be packaged in verysmall sizes having low weight which, in association with their otheradvantages, makes them ideal for use in portable or wearable CPAPdevices.

However, compressors used in CPAP therapy must be capable of generatingdifferent flow rates depending upon the type of respiratory treatment tobe provided as well as the respiratory condition and physiological sizeof the patient. For example, patients undergoing CPAP treatment canrange from pre-term infants, neonates and pediatric patients up tofull-grown adult patients. As may be appreciated, the pressurized gasrequirements of a neonatal patient differ markedly from the pressurizedgas requirements of a full grown adult. Flow settings for neonates canbe as low as 2 liters per minute (LPM) at pressures as low as 5 cm H₂0as compared to the flow settings for a full grown adult patientrequiring flow rates of up to 120 LPM and pressure settings of 20 cm H₂0and higher.

As a result of these differing flow requirements, different compressorassemblies are designed for use with a certain range of flow settings.The compressor assemblies are optimized to produce the desired flowrequirements at maximum operating efficiency and with minimal powerconsumption. In this regard, a common practice in the industry is todevelop and manufacture a specific compressor assembly which producesoptimal flow characteristics for a specific set of patient types and/orflow settings. As may be appreciated, the need to design, test andmanufacture completely different configurations of compressor assembliesfor different patients having differing flow requirements substantiallyincreases the overall cost of CPAP devices.

As can be seen, there exists a need in the art for a compressor assemblyhaving the capability to efficiently produce a broad range of flowcharacteristics (i.e., flow rate, pressure) for specific patientapplications at a substantially reduced cost to the manufacturer and,ultimately, at a reduced cost to the consumer.

BRIEF SUMMARY

The above-mentioned needs associated with compressor assemblies havingdiffering flow capabilities is specifically addressed by the presentinvention which provides a modular compressor assembly. The compressorassembly includes a baseline or common motor assembly having a preset orfixed configuration but which is mountable to blower housings of variousconfigurations (e.g., different cross-sectional geometries) such thatthe compressor assembly may be used to provide a variety of differentrespiratory treatment modalities to patients of varying size.Advantageously, the interchangeability of the blower housing isfacilitated by a universal engagement mechanism which conveniently andeffectively allows for mounting of different blower housings on asingle, common motor assembly.

In one embodiment, the motor assembly includes a stator housingcontaining a stator assembly. A rotor magnet is rotatably disposedwithin and coupled to the stator assembly. The compressor assemblyfurther includes an impeller which may be selectable from among aplurality of impellers each having a different geometry and which isformed complimentary to the blower housing. The impeller is configuredto be mountable to and rotatable in unison with the rotor magnet. Theimpeller rotates within the blower housing and draws air into the blowerinlet after which the air is compressed and discharged at a bloweroutlet.

The blower housing may comprise upper and lower housing portions eachconfigured to be engageable to one another at a perimeter joint such asby adhesive bonding, sonic welding or any other suitable means. At leastone of the upper and lower housing portions includes the engagementmechanism to allow interchangeable mounting of the blower housing to thecommon motor assembly.

In one embodiment, the engagement mechanism may comprise a locating ringformed around an outer circumference of the stator housing. The lowerhousing portion may include a complimentary annular groove extendingaround an inner wall of the lower housing portion. The annular groove ispreferably sized and configured complimentary to the locating ring suchthat the lower housing portion is maintained in fixed position relativeto the motor assembly.

The motor assembly may be provided in any operational configuration butis preferably configured as a three-slot/two-pole brushless D.C. motor.The stator assembly preferably includes a stator bore for receiving therotor magnet therewithin. The blower housing and stator housingcollectively form an annular chamber or volute which defines a housinginterior surface of the blower housing. The stator assembly includes abearing assembly comprising upper and lower bearings disposed within thestator bore. The bearing assembly is configured to rotatably support therotor magnet and the impeller relative to the stator assembly.

The impeller preferably includes a plurality of upwardly extending vaneseach having a free edge defining a relatively small air gap with thehousing interior surface. The impeller and bearing assembly arepreferably sized and configured such that the air gap is maintained at aminimum (e.g., less than approximately 0.006 inches) during rotation ofthe impeller. In this manner, the compressor assembly minimizesaerodynamic losses such as vane-to-vane losses or losses resulting fromparasitic fluid eddies which can reduce the operating efficiency of thecompressor assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present invention will become moreapparent upon reference to the drawings wherein:

FIG. 1 is an exploded perspective view of a modular compressor assemblycomprising a common motor assembly releasably engageable to a blowerhousing selectable from among a variety of blower housings each having adifferent configuration;

FIG. 2 is a perspective view of the modular compressor assembly in anassembled state;

FIG. 3 is a perspective view of the modular compressor assembly lookingat an underside thereof;

FIG. 4 is a top view of the modular compressor assembly;

FIG. 5 is a cross-sectional view of the modular compressor assemblytaken along lines 5-5 of FIG. 4 and illustrating a locating ring formedon a stator housing and an annular groove formed in the blower housing;and

FIG. 6 is an exploded sectional view of the modular compressor assemblyillustrating the locating ring configured to be engageable to theannular groove and further illustrating the interconnectivity of thelower and upper housing portions along a perimeter joint.

DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes ofillustrating preferred embodiments of the present invention and not forpurposes of limiting the same, shown in FIGS. 1 to 6 is a modularcompressor assembly 10 which, in its broadest sense, comprises abaseline or common motor assembly 30 configured to be engageable toblower housings 12 of differing geometry to achieve differing flowcharacteristics using the same common motor assembly 30. Toward thisend, the compressor assembly 10 includes an engagement mechanism 128 toallow for mounting of the motor assembly 30 to the blower housings 12.

In this manner, the compressor assembly 10 may be economicallymanufactured and capable of producing a broad range of flowcharacteristics (i.e., different flow rates and pressures) for specificpatient applications at a substantially reduced cost. Advantageously,the common motor assembly 30 may include oversized bearings in order tomaintain the operating efficiency of the compressor assembly 10 and tominimize vibration and/or noise regardless of the size of the impeller56 or speed of rotation thereof.

Referring to FIGS. 1 to 6, shown is the modular compressor assembly 10constructed in a manner such that the compressor assembly 10 has arelatively short axial length (i.e., short height) and relatively smalloverall diameter. The miniaturized or compact configuration of thecompressor assembly 10 is due in part to the arrangement of the commonmotor assembly 30 which includes a stator housing 34 containing a statorassembly 32 and which includes a stator bore 38 formed therewithin. Thecommon motor assembly 30 further includes a rotor magnet 106 disposedwithin the stator bore 38 and which is rotatably coupled to the statorassembly 32 by means of a pair of upper and lower bearings 88, 90.

In this regard, the configuration shown in FIGS. 1 and 6 illustrates anarrangement wherein the rotor magnet 106 is disposed radially inwardlyfrom the stator assembly 32 as opposed to the configuration shown incommonly-owned U.S. Pat. No. 7,012,346, issued to Hoffman et al, theentire contents of which is incorporated by reference herein, whereinthe rotor magnet assumes a ring shape which is disposed radiallyoutboard of the stator assembly.

Referring still to FIGS. 1 to 6, the modular compressor assembly 10further comprises an impeller 56 which is configured to be mountable toand rotatable with the rotor magnet 106. The impeller 56 is fixablymounted onto a motor shaft 78 such as by press fit or other suitablemeans. The impeller 56 rotates with the rotor magnet 106 which iscoupled to the stator assembly 32 by upper and lower bearings 88, 90.

The impeller 56 draws air into an annular blower inlet 20 which iscollectively defined by an upper housing neck 104 and a hub portion 60of the impeller 56 as best seen in FIG. 5. Air drawn into the blowerinlet 20 is directed downwardly in an axial direction whereafter thevanes 64, 66 compress the air as the air moves laterally outwardly alongvane passages defined by the vanes 64, 66. The compressed air is forcedinto the annular chamber 24 or volute which is defined by the blowerhousing 12. The compressed air is then discharged from the blowerhousing 12 at a blower outlet 22 which is preferably located on aperipheral edge of the blower housing 12.

In one embodiment, the motor assembly 30 is configured as athree-slot/two-hole brushless D.C. motor assembly 30 wherein each of theslots of the stator assembly 32 is arranged circumferentially anddefines a number of rotor teeth or core sections 42. Each of the coresections 42 has layers of electrical winding wound thereabout. It shouldbe pointed out that the stator assembly 32 is not limited to thethree-slot arrangement illustrated in the figures but may be providedwith any number of slots (i.e., core sections 42) with the rotor magnet106 being provided with a complimentary number of poles. In addition,the motor assembly 30 may be provided in a conventional brushedconfiguration.

The brushless D.C. motor assembly 30 preferably includes an intelligentelectronic controller or commutator 50 which is operative tosequentially commutate or provide current to the core sections 42 of thestator assembly 32 at the appropriate time to induce and maintainrotation of the rotor magnet 106 and, hence, the impeller 56. In thisregard, the motor assembly 30 may further include a means for sensingthe position and/or orientation of magnetic poles 46 of the rotatingrotor magnet 106. For example, position sensors 48 such as Hall sensorsmay be included in the motor assembly 30 and which are configured tocooperate with the electronic controller to regulate the speed of themotor assembly 30.

Referring briefly to FIGS. 3 and 5, the electronic controller may bemounted on a printed circuit board (PCB 54) and may include electricalcontacts 52 for connecting to and controlling the motor assembly 30. Thecontroller may further be integrated with the PCB 54 which itself mayfurther include the position sensors 48 (e.g., Hall sensors) to sensethe relative positions and speed of the magnetic poles 46 of therotating rotor magnet 106 relative to the stator assembly 32. The PCB 54may be located within an annular recess 28 disposed on an underside ofthe motor assembly 30 and which is collectively defined by a lowerhousing portion 14 and the stator housing 34 as best seen in FIGS. 3 and5.

Referring to FIGS. 1, 5 and 6, the compressor assembly 10 furthercomprises the blower housing 12 which is selectable from among aplurality or variety of different blower housings 12 each having adifferent cross-sectional geometry, shape or size. As can be seen inFIG. 1, the blower housing 12 may be comprised of upper and lowerhousing portions 16, 14 which are configured to be engageable to oneanother such as along a perimeter joint 18 as best seen in FIGS. 5 and6. More specifically, the upper and lower housing portions 16, 14 may besecured to one another along the perimeter joint 18 such as by adhesivebonding, sonic welding or any other suitable means including mechanicalsecurement.

The upper and lower housing portions 16, 14 are preferably formed asseparate components from the motor assembly 30 in order to provide themodular aspect to the compressor assembly 10. In this regard, the upperand lower housing portions 16, 14 may be provided in a variety ofdifferent configurations but which are each configured to be engageableto the single, common motor assembly 30 such that the compressorassembly 10 is capable of providing different flow profiles as isrequired for different patients and different types of treatment.

Toward this end, the impeller 56 is selectable from among a plurality ofdifferent impeller 56 configurations. Each impeller 56 configuration isformed complimentary to a set of upper and lower housing portions 16, 14in order to achieve the desired flow characteristics (i.e., flow rateand/or pressure) with maximum compressive efficiency. Furtherfacilitating the modular aspect of the compressor assembly 10 is theexteriorly accessible location of the PCB 54 on the underside of theblower housing 12. The accessible location of the PCB 54 allows forconvenient substitution of the electronic controller and/or commentatorwith electronic components having operating characteristics that arecomplimentary to the particular impeller 56 and blower housing 12combination.

Referring still to FIGS. 1, 5 and 6, mating of the blower housing 12 tothe common motor assembly 30 is facilitated by the engagement mechanism128 which is disposed on the stator housing 34 and/or the blower housing12. As will be described in greater detail below, the engagementmechanism 128 may be integrally formed in at least one of the statorassembly 32 and/or upper and lower housing portions 16, 14. Each one ofthe stator assembly 32 and/or upper and lower housing portions 16, 14may be fabricated as separate components by injection molding or othersuitable manufacturing or molding process.

The stator assembly 32 may be constructed of a plurality of coresections 42 and associated electrical windings 44 integrally molded intothe stator housing 34. Housing apertures 40 may be strategically placedin the stator assembly 32 to eliminate warpage that may otherwise occurdue to uneven shrinkage or contraction during cooling of the injectionmolded stator assembly 32. In this manner, the molded parts may befabricated with precise dimensional control which facilitates finalassembly of the compressor assembly 10 and allows for extremely closeoperational tolerances that contribute to the efficiency of the modularcompressor assembly 10.

Furthermore, precise control of the dimensional characteristics of thecompressor assembly 10 facilitates assembly of the individual componentssuch as bonding of the upper and lower housing portions 16, 14 at theperimeter joint 18. In addition, precise dimensional control of themotor assembly 30 and the blower housing 12 maintains the relativelynarrow air gap 76 between the rotating impeller 56 and the housinginterior surface 26 during the relatively high speeds (e.g., up to35,000 RPM) at which the impeller 56 may rotate.

Referring particularly to FIG. 5, the bearing assembly 86 may beintegrated into the manufacturing process of the stator assembly 32wherein upper and lower bearing carriers 92, 94 are integrally moldedwith the stator assembly 32. As can be seen in FIG. 5, the upper andlower bearing carriers 92, 94 are preferably disposed in spaced relationat upper and lower ends of the stator assembly 32. In consideration ofthe modular aspect of the compressor assembly 10, the upper and lowerbearings 88, 90 are preferably over-sized considering the relatively lowinertial and rotational loads imposed thereupon at low flow rates andpressures.

However, by providing the upper and lower bearings 88, 90 in arelatively large size reduces wear of the bearings over time such thatthe useful life of the compressor assembly 10 is extended. Furthermore,the use of over-sized upper and lower bearings 88, 90 facilitates thesubstitution of a larger impeller 56 as may be required for increasedflow capacity of the compressor assembly 10. Even further, the use ofover-sized upper and lower bearings 88, 90 minimizes losses incompressive efficiency and also minimizes the development of vibrationand/or noise over time due to normal wear and tear.

Referring briefly to FIGS. 3 and 5, assembly and disassembly of thecompressor assembly 10, as may be required for repair or periodicmaintenance, is facilitated by the removability of the bearing assembly86 and rotor magnet 106 from an underside of the stator assembly 32. Inone embodiment, the stator assembly 32 may include a retainer element 98such as a simple snap ring which is engageable to a corresponding grooveformed in a lower housing flange 102. As best seen in FIG. 3, the lowerhousing flange 102 extends axially downwardly from the lower housingportion 14 and the snap ring is engageable into the groove formedtherein. The motor assembly 30 preferably includes a biasing element 100interposed between the retainer element 98 and the lower bearing 90 inorder to upwardly bias the bearing assembly 86, rotor magnet 106 and,motor shaft 78 and thereby minimize the air gap 76 between the freeedges 68 of the impeller 56 and the housing interior surface 26.

The biasing element 100 may be configured as a wave spring, acompression spring or any other suitable biasing configuration. Thebiasing element 100 bears against the retainer element 98 (i.e., snapring) and pushes upwardly against an outer bearing race of the lowerbearing 90 such that the lower bearing 90 is biased upwardly against theupper bearing carrier 92. Each one of the upper and lower bearings 88,90 is comprised of inner and outer bearing races which areinterconnected by a plurality of ball bearings.

As best seen in FIG. 5, the motor shaft 78 defines a shaft axis B andincludes distal and proximal ends 80, 82. A shaft shoulder 84 is formedadjacent the distal end 80 of the motor shaft 78 to provide a surfaceagainst which the rotor magnet 106 may bear on one side of the shaftshoulder 84 and against which the lower bearing 90 assembly 86 may bearagainst an opposing side of the shaft shoulder 84. A spacer 96 may beinterposed between the rotor magnet 106 and the upper bearing 88assembly to maintain spacing between the upper and lower bearings 88,90. More specifically, the spacing between the upper and lower bearings88, 90 is maximized in order to better maintain coaxial alignment of themotor shaft 78 axis with a stator axis A of the stator assembly 32.

Referring to FIGS. 5 and 6, the impeller 56 is adapted to be mounted ona proximal end 82 of the motor shaft 78. The impeller 56 includes arounded or dome-shaped hub portion 60 having an impeller bore 58extending at least partially therethrough. A conically shaped rampportion 70 extends circumferentially around the hub portion 60. The hubportion 60 is disposed in close rotating relationship with an uppersurface of the stator assembly 32 in order to minimize total volumeoccupied by the impeller.

As best seen in FIGS. 1, 5 and 6, the impeller 56 includes a pluralityof the vanes 64, 66 extending upwardly from the ramp portion 70. Thevanes 64, 66 are disposed in spaced relation to one another on the rampportion 70 and are preferably non-radially oriented. The vanes 64, 66define vane passages. As illustrated, the vanes 64, 66 are shown asbeing generally aft facing in that the outer edges of the vanes point ina direction opposite the rotational direction of the impeller 56.

In one embodiment, the vanes 64, 66 alternate between full-length vanes66 and partial-length vanes 64 to minimize the generation of pressurepulsations at the outer perimeter which can otherwise occur inrelatively small blowers having a limited quantity of vanes 64, 66.However, the alternating partial length and full-length vanes 64, 66maximize the overall area at the blower inlet 20 while minimizing thegeneration of pressure pulses at the downstream end of the vanes 64, 66due to the effective increase in the vane quantity at the outlet end ofthe vane passages.

Each one of the vanes 64, 66 defines a free edge 68 which is sized andconfigured complimentary to the housing interior surface 26 such thatthe impeller 56 rotates in extremely close proximity thereto in order tominimize the generation of energy-reducing fluid eddies or turbulence.Such eddies may be characterized as aerodynamic or parasitic energylosses which otherwise occur in conventional centrifugal blowers of theprior art. As is known in the art, parasitic fluid eddies limit thepressure and flow rate capability of centrifugal blowers and can alsocontribute to the generation of unwanted acoustic energy (i.e., noise)by the compressor assembly 10.

However, depending upon the particular configurations of the impeller 56and blower housing 12 as used in conjunction with the common motorassembly 30, the height of the vanes 64, 66 is preferably optimized forthe pressure and flow rate of the compressor assembly 10. Due to theoptimized vane height and extremely small air gap 76 between the freeedges 68 of the vanes 64, 66 and the housing interior surface 26, thecompressor assembly 10 is capable of effectively producing the desiredflow rate and pressure output with minimum input power at the motorassembly 30 and minimal generation of noise and vibration.

Referring to FIGS. 5 and 6, assisting in maintaining the air gap 76between the vanes 64, 66 and the blower housing 12 is the dimensionalprecision with which the impeller 56 is fabricated. More specifically,the impeller 56 is preferably statically and dynamically balanced byremoving material from the downwardly turned lip portion 72 of theimpeller. As best seen in FIG. 5, the lip portion 72 extends about aperimeter of the ramp portion 70 and is configured to fit within anannular undercut 36 formed along an upper perimeter edge of the statorhousing 34. The annular undercut 36 and lip portion 72 collectivelydefine a narrow lip gap 74 which allows the outer surface of the lipportion 72 to lie generally flush with the outer wall 132 of the statorhousing 34.

Referring to FIGS. 1, 5 and 6, the precise geometric relationshipbetween the motor assembly 30 and the blower housing 12 is facilitatedby the engagement mechanism 128 which is disposed on the stator housing34 and/or the blower housing 12. As was earlier mentioned, theengagement mechanism 128 allows for interchangeable mounting ofdifferent blower housing 12 configurations with the common motorassembly 30 in order to achieve different flow characteristics of thecompressor assembly 10. In one embodiment, the engagement mechanism 128may be integrated into the lower housing portion 14 and the statorhousing 34.

The engagement mechanism 128 may be embodied as a locating ring 130extending about a circumference of an outer wall 132 of the statorhousing 34. A complimentary annular groove 134 may be formed on an innerwall 136 of the lower housing portion 14 and is preferably sized andconfigured to receive the locating ring 130 therewithin. Although shownas a contiguous circumferential ring element, the locating ring 130 maybe provided in a variety of alternative shapes, sizes andconfigurations. For example, the locating ring 130 may be comprised of aplurality of angularly spaced ring segments disposed around the outerwall 132 of the stator housing 34. In another configuration, theengagement mechanism 128 may be configured as a plurality of angularlyspaced bosses extending outwardly from the outer wall 132 of the statorhousing 34. The inner wall 136 of the lower housing portion 14preferably includes complimentary features configured to receive and/orengage the features formed on the outer wall 132 of the stator housing34.

The modular aspect of the compressor assembly 10 provides a convenientmeans for interchangeability of blower housing 12 configurations withthe common motor assembly 30. For example, FIGS. 5 and 6 illustratedifferent blower housing 12 configurations mounted on the common motorassembly 30. More specifically, the common motor assembly 30 illustratedin FIG. 5 has the same overall configuration (i.e., same size and shape)as the common motor assembly 30 illustrated in FIG. 6 although theblower housing 12 in FIG. 6 is of a larger size (i.e., larger outerdiameter) than the blower housing 12 illustrated in FIG. 5. Because ofthe size and configuration differences in the blower housings 12, thecompressor assemblies in FIGS. 5 and 6 are capable of different flowrates. Preferably, each of the blower configurations is optimized foruse with patients having different respiratory needs.

Referring briefly to FIGS. 2 to 4, the blower housing 12 may optionallyinclude at least one and, more preferably, three angularly spacedsuspension mounts 108 extending laterally outwardly from at least one ofthe upper and lower housing portions. The suspension mounts 108 aresized and configured to support the compressor assembly 10 whileattenuating or dampening vibration (e.g., radial or axial) generated bythe compressor assembly 10. Preferably, the suspension mounts 108 arelocated adjacent to the perimeter joint 18 and are configured to preventor mitigate propagation of vibration from the compressor assembly 10 toa mounting frame 120 or housing.

Each of the suspension mounts 108 is preferably configured as aserpentine-shaped spring member 110 which has a terminus end 112preferably adapted to mount the compressor assembly 10 to mounting slotsformed in a mounting frame or housing. Each of the terminus ends 112 ofthe spring member 110 preferably includes a generally axially-orientedtab member 118. Each one of the spring members 110 extends laterallyoutwardly from the blower housing 12 wherein the spring member 110 formsa 90° bend 114. The spring member 110 may also include a pair of 180°bends 116 prior to terminating at an additional 90° bend 114 at theterminus end 112 of the spring member. However, any number of turns maybe included in the spring member 110 in order to provide the desireddampening or attenuating characteristics.

Referring briefly to FIG. 1, also included in the present invention is amethod of constructing a modular compressor assembly 10. The methodcomprises the steps of forming a stator assembly 32 having upper andlower bearing carriers 92, 94 and a plurality of core sections 42. Aswas earlier mentioned, each one of the core sections 42 preferablyextends radially outwardly from the stator bore 38 and includes awinding to allow for sequential magnetization of the core sections 42and rotation of the motor assembly 30.

The method further comprises molding the stator housing 34 to includethe stator bore 38 such that the stator housing 34 encapsulates thestator assembly 32 and coaxially confines the upper and lower bearingcarriers 92, 94 relative to the stator bore 38. The stator bore 38defines the stator axis A. The method further comprises forming themotor shaft 78 which preferably includes the shaft shoulder 84 locatedon a distal end 80 thereof. The rotor magnet 106 is preferably fixablymounted to the motor shaft 78 such that the rotor magnet 106 is disposedin abutting contact with the shaft shoulder 84. Assembly of the motorshaft 78 may further include installation of the spacer 96 followed bymounting of the upper bearing 88.

The upper bearing 88, spacer 96 and rotor magnet 106 are insertable intothe stator bore 38 such as from an underside of the compressor assembly10 as best seen in FIG. 2. The lower bearing 90 is preferably installedon the motor shaft 78 and placed in abutting contact with an undersideof the shaft shoulder 84. The biasing element 100 and retainer element98 are then installed within the lower housing flange 102 as best seenin FIGS. 3 and 5. The method further comprises securing the impeller 56on the proximal end 82 of the motor shaft 78 such as by press fit untila mounting boss 62 of the impeller 56 is in abutting contact with theupper bearing 88. Position sensors 48 (e.g., Hall sensors), PCB 54 andother electronic components may be installed on the underside of themotor assembly 30 as shown in FIG. 3.

Importantly, the method further includes forming the engagementmechanism 128 on at least one of the stator housing 34 and the blowerhousing 12. For example, the engagement mechanism 128 may be formed byforming the locating ring 130 on the outer wall 132 of the statorhousing 34 as best seen in FIG. 1. The step of forming the engagementmechanism 128 may further comprise forming the annular groove 134 on theinner wall 136 of the lower housing portion 14 wherein the annulargroove 134 is sized and configured complimentary to the locating ring130 on the stator housing 34.

The method of constructing the compressor assembly 10 may include matingthe lower housing portion 14 to the stator housing 34 by engaging thelocating ring 130 to the annular groove 134. As mentioned above, theengagement mechanism 128 is not limited to the locating ring 130 but maytake a variety of alternative configurations including ring segments, orother mechanical features. The construction of the compressor assembly10 may include the step of statically and dynamically balancing theimpeller 56 such that the air gap 76 between the free edges 68 of thevanes 64, 66 and the housing interior surface 26 s is preferablymaintained at less than approximately 0.006 inches and, more preferably,at approximately 0.002 inches. Following the balancing of the impeller,the upper housing portion 16 may be secured to the lower housing portion14 at the perimeter joint 18 by any suitable means such as adhesivebonding, sonic welding or mechanical attachment. The upper and lowerhousing portions 16, 14 collectively define the annular chamber 24(i.e., volute).

The description of the various embodiments of the present invention arepresented herein to illustrate preferred embodiments of the inventionand other inventive concepts as may be otherwise variously embodied andemployed. The claims are intended to be construed to include suchvariations except insofar as limited by the prior art.

1. A modular compressor assembly comprising: a common motor assemblyhaving a stator housing containing a stator assembly and having a rotormagnet disposed within and rotatably coupled to the stator assembly; animpeller configured to be mountable to and rotatable with the rotormagnet; a blower housing selectable from among a plurality of blowerhousings each having a different cross sectional geometry; an engagementmechanism disposed on at least one of the stator housing and the blowerhousing to allow interchangeable mounting of the blower housing to thecommon motor assembly to achieve different flow characteristics of thecompressor assembly.
 2. The compressor assembly of claim 1 wherein theimpeller is selectable from among a plurality of impellers each having adifferent geometry and being formed complementary to at least one of theblower housing cross sectional geometries.
 3. The compressor assembly ofclaim 1 wherein the blower housing comprises upper and lower housingportions configured to be engageable to one another at a perimeterjoint.
 4. The compressor assembly of claim 3 wherein the engagementmechanism is formed on at least one of the upper and lower housingportions.
 5. The compressor assembly of claim 4 wherein the engagementmechanism comprises: a locating ring extending around a circumference ofan outer wall of the stator housing; and an annular groove extendingaround an inner wall of the lower housing portion and being sized andconfigured complementary to the locating ring.
 6. The compressorassembly of claim 4 wherein at least one of the upper and lower housingportions includes a plurality of suspension mounts extending laterallyoutwardly from a perimeter thereof and being sized and configured tosupport the compressor assembly.
 7. The compressor assembly of claim 1wherein: the motor assembly is configured as a three-slot/two-polebrushless D.C. motor; the stator assembly having a stator bore formedtherethrough; the rotor magnet being rotatable within the stator bore.8. The compressor assembly of claim 1 wherein: the blower housing andstator housing collectively defining an annular chamber having a housinginterior surface; the stator assembly including a bearing assemblydisposed within the stator bore and being configured to rotatablysupport the impeller; the impeller including a plurality of upwardlyextending vanes each having a free edge and defining an air gap with thehousing interior surface; the impeller and bearing assembly beingconfigured such that the air gap is maintained at less thanapproximately 0.006 inches during rotation of the impeller.
 9. A blowerhousing for a modular compressor assembly having a stator housingcontaining a stator assembly and a rotor magnet rotatably within thestator assembly, the blower housing comprising: upper and lower housingportions configured to be engageable to one another at a perimeterjoint, at least one of the upper and lower housing portions beingconfigured to be removably mountable to the stator housing.
 10. Theblower housing of claim 9 wherein: the stator housing includes an outerwall having a locating ring extending around a circumference of theouter wall; the lower housing portion including an inner wall having anannular groove extending therearound and being sized and configured tobe removably engageable to the locating ring for mating the lowerhousing portion to the stator housing.
 11. The blower housing of claim 9wherein the lower housing portion includes a plurality of suspensionmounts extending laterally outwardly from a perimeter thereof and beingsized and configured to support the modular compressor assembly.
 12. Theblower housing of claim 9 wherein: the motor assembly is configured as athree-slot/two-pole brushless D.C. motor; the stator assembly having astator bore formed therethrough; the rotor magnet being rotatable withinthe stator bore.
 13. The blower housing of claim 9 wherein: the blowerhousing and stator housing collectively define an annular chamber havinga housing interior surface; the stator assembly including a bearingassembly disposed within the stator bore and being configured torotatably support the impeller; the impeller including a plurality ofupwardly extending vanes each having a free edge and defining an air gapwith the housing interior surface; the impeller and bearing assemblybeing configured such that the air gap is maintained at less thanapproximately 0.006 inches during rotation of the impeller.
 14. A methodof constructing a modular compressor assembly, comprising the steps of:forming a stator assembly having upper and lower bearing carriers and aplurality of angularly spaced core sections each having a windingextending therearound; molding a stator housing with a stator bore suchthat the stator housing encapsulates the stator assembly and coaxiallyconfines the upper and lower bearing carriers relative to the statorbore; forming a motor shaft; mounting a rotor magnet on the motor shaft;disposing upper and lower bearings between the motor shaft and the upperand lower bearing carriers such that the motor shaft is coaxial with thestator bore; forming an impeller having a plurality of elongate vaneseach defining a vane height and having a free edge; securing theimpeller to the motor shaft; forming a lower housing portion having anengagement mechanism configured to facilitate removable engagement ofthe lower housing portion to the stator housing; securing the lowerhousing portion to the stator housing; forming an upper housing portionconfigured to be mateable to the lower housing portion; and securing theupper housing portion to the lower housing portion such that the upperand lower housing portions collectively define an annular chamber havinga housing interior surface.
 15. The method of claim 9 wherein the statorassembly and rotor magnet collectively define a motor assembly, themethod further comprising the steps of: forming a locating ring on anouter wall of the stator housing; forming an annular groove on an innerwall of the lower housing portion, the annular groove being formedcomplementary to the locating ring; and mating the lower housing portionto the stator housing by engaging the locating ring to the annulargroove.
 16. The method of claim 9 wherein the free edges of each of thevanes defines an air gap with the housing interior surface, the methodfurther comprising the step of: balancing the impeller by removingmaterial therefrom such that the air gap is maintained at less thanapproximately 0.006 inches.